Noise suppressing devices such as an active noise controller and an echo canceller exist (refer to, for example, Japanese Unexamined Patent Application Publication Nos. 8-123444 and 10-207473). When noise occurs, such noise suppressing devices suppress the noise by generating sounds canceling the noise other than voices.
In general, in an active noise controller, error microphones and loud speakers outputting canceling sounds canceling noise are disposed at given positions. An active noise controller obtains the respective transfer characteristics of sounds (noise) between noise sources and error microphones on the basis of sound signals output from the noise sources and sound signals obtained by the error microphones. Then, the active noise controller generates canceling sounds minimizing sounds (noise) obtained by the error microphones on the basis of the obtained transfer characteristics. The active noise controller outputs such canceling sounds from loud speakers to suppress noise received at the respective positions of the error microphones by using the canceling sounds from the loud speakers.